Prior art optical microcavities are resonators that typically have at least one dimension (herein typically the effective optical length of the cavity) on the order of an optical wavelength. It has been recognized that such resonators not only are interesting for fundamental research purposes but also hold technological promise for constructing novel kinds of light emitting devices. See, for instance, H. Yokoyama, Science, Vol. 256, pp. 66-70, which inter alia discloses a microcavity structure that contains a dye solution. See also Y. Yamamoto et al., Physics Today, pp. 66-73, June 1993. Possible applications of such microresonator light emitting devices are, for instance, in the fields of flat panel displays, back lights, optical interconnects, optical fiber communications and LED printing.
U.S. patent application Ser. No. 08/156,217, filed by us on Nov. 22, 1993 now U.S. Pat. No. 5,405,710 and incorporated herein by reference, discloses an apparatus that comprises at least two microcavity light emitters that differ in their cavity length, such that the microcavities emit radiation of a first and a second wavelength, respectively. See also A. Dodabalapur et al., Applied Physics Letters, Vol. 64(19), p. 2486.
At least some technological fields require emission of light of a specified apparent color, e.g., white. Such emissions are typically achieved through mixing of the emission from two or more different types of LED. See, for instance, K. Murata, Display Devices, pp. 47-50, 1992. Alternatively they can be achieved by incorporation of fluorescent dyes of different color into an organic LED. See J. Kido et al., Applied Physics Letters, Vol. 64 (7), p. 815 (1994), and G. E. Johnson et al., SPIE, Vol. 1910, p. 6. Exemplarily, devices that emit white light would be of interest for, e.g., low voltage portable backlit displays.
Known devices that emit white light or other mixed colors are not entirely satisfactory for technological applications such as displays for lap-top computers. For instance, some prior art displays are typically difficult to manufacture, and others emit over a broad wavelength range, with only relatively small peaks at predetermined wavelengths superimposed on a broad continuum. See, for instance, FIG. 2 of J. Kido et al., op. cit. Thus, a light emitting device that can emit light of a predetermined apparent color, exemplarily substantially white, and that can be manufactured relatively easily and economically, would be of considerable interest. This application discloses such a device.